Cryogenic rectification, such as the cryogenic rectification of feed air, requires the provision of refrigeration to drive the separation. Generally such refrigeration is provided by the turboexpansion of a process stream, such as, for example, a portion of the feed air. While this conventional practice is effective, it is limiting because any change in the requisite amount of refrigeration inherently affects the operation of the overall process. It is therefor desirable to have a cryogenic rectification system wherein the provision of the requisite refrigeration is independent of the flow of process streams for the system.
One method for providing refrigeration for a cryogenic rectification system which is independent of the flow of internal system process streams is to provide the requisite refrigeration in the form of cryogenic liquid brought into the system. Unfortunately such a procedure is very costly.
Accordingly it is an object of this invention to provide an improved cryogenic rectification system wherein the provision of at least some of refrigeration for the separation is independent of the turboexpansion of process streams and does not require the provision of exogenous cryogenic liquid to the system.